Have 2012 F150 Ecoboost King Ranch. RPM's fluctuate up and down rapidly when accelerating. Once up to speed, it goes away. Seems to do it more when truck is cold (not warmed up). When towing something, it feels and sounds like the truck is going to fall apart. No computer error codes detected. Everyone is at a complete loss. Truck is under extended warranty and had been at the dealership now for going on 2 months. they still have no idea and have only replaced exhaust manifold. Could really use some advise on what the issue may be and what to do to get this fixed quickly. Truck was purchased for towing purposes and they gave me a car as a loaner. have missed 2 camping trips due to not having a truck.

 

How many miles? Have you ever changed the plugs on it? Mine idles like it is camed and always has.

 

Can you accelerate under very light throttle and not have this happen? It sounds like a boost leak. The best way to find a leak is to smoke test the intake tract. Look for hoses that are cracked or loose. I've also seen rubber boots that are cracked and only open up under pressure. That one was a pain to find.

 

2012, as I recall, that was the YM that we had issues with the torque converter and it did the same thing. Might have them check the transmission too. Ours did not code up either, FWIW.